#include <jni.h>
#include <string.h>
//将java字符串转换为c语言字符串（工具方法）
char*   Jstring2CStr(JNIEnv*   env,   jstring   jstr)
{
    char*   rtn   =   NULL;
    jclass   clsstring   =   (*env)->FindClass(env,"java/lang/String");
    jstring   strencode   =   (*env)->NewStringUTF(env,"GB2312");
    jmethodID   mid   =   (*env)->GetMethodID(env,clsstring,   "getBytes",   "(Ljava/lang/String;)[B");
    jbyteArray   barr=   (jbyteArray)(*env)->CallObjectMethod(env,jstr,mid,strencode); // String .getByte("GB2312");
    jsize   alen   =   (*env)->GetArrayLength(env,barr);
    jbyte*   ba   =   (*env)->GetByteArrayElements(env,barr,JNI_FALSE);
    if(alen   >   0)
    {
        rtn   =   (char*)malloc(alen+1);         //"\0"
        memcpy(rtn,ba,alen);
        rtn[alen]=0;
    }
    (*env)->ReleaseByteArrayElements(env,barr,ba,0);  //
    return rtn;
}
JNIEXPORT jstring JNICALL Java_com_ykm_serialport_JniUtil_encode
        (JNIEnv * env, jobject obj, jstring text, jint length){
    char* cstr = Jstring2CStr(env, text);
    int i;
    for(i = 0;i<length;i++){
        *(cstr+i) += 1; //加密算法，将字符串每个字符加1
    }
    return (*env)->NewStringUTF(env,cstr);
}
JNIEXPORT jstring JNICALL Java_com_ykm_serialport_JniUtil_decode
        (JNIEnv * env, jobject obj, jstring text, jint length){
    char* cstr = Jstring2CStr(env, text);
    int i;
    for(i = 0;i<length;i++){
        *(cstr+i) -= 1;
    }
    return (*env)->NewStringUTF(env, cstr);
}